1. Field of the Invention
The present invention relates to a stamp having a handle and a rubber letter (figure) on the top end of the handle, and more particularly to a stamp connectable in a series so as to print a series of letters or figures.
2. Description of the Prior Art
To connect one stamp to another so as to achieve a series of letters or figures, a problem is involved in aligning the letters or figures on the different stamps. To solve this problem there have been many proposals, among which is a stamp disclosed in Japanese Utility Model Publication (examined) No. 54(1979)-5054. This stamp has a lengthwise groove or narrow width on one side and a lengthwise projection on the other side so that the projection in one stamp fits in the groove of another to form a unity. The united stamps are covered with a cap so as to secure the unit thereof.
This prior art stamp secures a firm unity of unit stamps, and avoid misalignment of the letters (or figures). However the connection of unit stamps requires a lot of labor, and a cap is additionally required, which leads to the increased cost.
To solve the problem pointed out above another proposal is made, which will be described by reference to FIG. 11:
The illustrated stamp 1 has a handle 2 which has a lengthwise recess 10 of relatively large size on one side 2a and a lengthwise projection 11 on the opposite side 2b, the projection being insertable in the recess 10. When the projection 11 is fitted in the recess 10, the two stamps 1 are connected side by side to form a series of figures, such as 12 or 56. When three stamps are united in this way, the resulting figure will be a three-digit figure, such as 123 or 568. The relatively large size of recess and projection secures a firm connection of the stamps with less possibility of misalignment.
A further proposal is disclosed in Japanese Utility Model Publication (unexamined) No. 53(1978)-34317. This is a modified version of the above-mentioned prior art stamp, and is provided with several recesses 10 and projections 11 on the respective sides.
The prior art illustrated in FIG. 11 dispenses with the use of a cap for securing the unity of the stamps connected together. This is an advantage in saving labor and cost. Nevertheless the exact alignment is difficult, and requires skill and experiment. Once the recess and projections have been fitted it is difficult to disassemble the connected stamps for re-adjustment or subsequent use. In addition, the relatively large recess and projection require a large space on the handle, thereby resulting in the increased size of the stamp. A pocket-size stamp allows of no space for the large recess and projection, and it is more difficult to produce them on such a limited space. When the recess and projection are of reduced sizes it becomes difficult to fit them, and after they are fitted the connection is likely to become loose.
The prior art stamp disclosed in the Japanese Utility Model Publication (unexamined) No. 53(1978)-34317 referred to above has solved this problem to some extent by providing several recesses and projections on the handle, but the fitting labor is multiplied for the increased number of them. In addition, the production of precise recesses and projections is difficult. This prior art method is only applicable to a relatively large size of stamp.
In connecting two or more stamps the problem is how to align the faces of letters or figures. If misalignment occurs some of the print is clear but the others are likely to be unclear. This problem is partly due to the loose connection of the stamps, and partly due to the uneven thickness of cushion 20 (FIG. 12). In general a rubber piece having a letter or figure is fixed to the handle 2 through a sponge 20 having a thickness of about 0.7 mm. However the sponge has uneven thickness in itself in a range of 0.5 to 1.3 mm. Such uneven thickness is unavoidably caused in the process of production. When a stamp is singly used no problem arises at all but when two or more stamps are used as a connected unity the misalignment of letter (or figure) faces is fatal to the print. The cushion 20 is jointed to the handle and the rubber 4 with an adhesive; the reference numerals 21 and 22 denote the adhesive layers, which means that two operational steps are required. This leads to the increased production cost.
Another problem involved in achieving series of stamps is the difficulty of ink absorption in the non-porous rubber pieces. To solve this problem the rubber is made of a porous rubber material which is capable of storing ink in the hollows (pores) defined in the porous material of the rubber. However porous rubber is supple and easily compressed against the paper, thereby squeezing the stored ink in excess. To prevent this problem the stamp is provided with any device for stopping an excessive force from applying to the handle. However it is difficult to provide stamps of the present invention with such devices. In addition, any aid must be furnished to the stamp for making up for the supple porous structure, which usually has a porosity of 60 to 90%.